Plugin setting typo in "fieldset_default_state" key's "all_expended" value

[sanak]

Problem
This is similar with Redmine core side typo.

• Defect #36149: Typo in CSS class for lists expander icon - Redmine

Expectation
all_expended should be replaced to all_expanded.

Note
Consider to add migration process in settings and user_preferences tables.
Here is the code snippet of settings table value.

setting = Setting.plugin_redmine_custom_fields_groups
if (
  setting.present? &&
  setting.has_key?('fieldset_default_state') &&
  setting['fieldset_default_state'] == 'all_expended'
)
  setting['fieldset_default_state'] = 'all_expanded'
  Setting.plugin_redmine_custom_fields_groups = setting
end

[sanak]

Close this because PR #30 was merged into next branch.